The resistance of PCBs to chemical and biological breakdown processes in nature makes them persistent in the environment. Many of the analytical techniques presently used for monitoring pollutants such as PCBs require expensive equipment and extensive pretreatment of environmental samples. Recognition of the difficulties inherent in classical analytical techniques has spurred the development of novel sensing systems that use a biological component as the sensory element. In that respect, the goal of this project is to develop their breakdown products (e.g., hydroxylated PCBs, chlorocatechols, etc.) that can be found in hazardous waste sites. The biosensing systems proposed are based on the use of recombinant bacteria that incorporate that catabolic pathways for PCBs along with the expression of reporter genes. In addition, sensors based on mammalian and test cells will also be developed by constructing systems where the expression of a reporter protein is coupled to the binding of the species of interest with the aromatic hydrocarbon receptor. Potential advantages of our proposed biosensory technology include economy, portability and the possibility of identifying and quantifying specific compounds directly in complex mixtures found in soil and groundwater samples.